mine

Egg at the leaf underside. The first part of the mine consists of a slender undulating corridor with a proportionally wide uninterrupted frass line, that leaves a clear transparant zone at either side. After a moult this corridor abruptly widens into a blotch, that develops into the opposite direction. The frass is concentrated here ia a diffuse central spot. The mine hardly ever crosses the midrib. Pupation outside the mine.